On the server:

sudo apt -y install munin apache2 libapache2-mod-fcgid

Enable the following settings in /etc/munin/munin.conf:

graph_strategy cgi
html_strategy cgi

Enable the following settings in /etc/munin/apache24.conf:

# Alias /munin /var/cache/munin/www
ScriptAlias /munin /usr/lib/munin/cgi/munin-cgi-html

Now run:

sudo a2enconf munin
sudo systemctl reload apache2

Now enable munin-node on your clients:

chroot /storage/spins/u20-x86/
apt -y update
apt -y upgrade
apt -y install munin-node

Add the following settings in /etc/munin/munin-node.conf:

allow ^192\.168\.11\.1$

Now add all your nodes to munin.conf:

sudo su -
cd /etc/munin
for d in `seq 10 250` ; do echo -e "[$d.localdomain]\n  address 192.168.11.$d\n  use_node_name yes\n"; done >> munin.conf